Vegetable fats and oils

Vegetable fats and oils are substances derived from plants that are composed of triglycerides. Nominally, oils are liquid at room temperature, and fats are solid; a dense brittle fat is called a wax. Although many different parts of plants may yield oil, in actual commercial practice oil is extracted primarily from the seeds of oilseed plants.

Culinary uses

Many vegetable oils are consumed directly, or used directly as ingredients in food - a role that they share with some animal fats, including butter and ghee. The oils serve a number of purposes in this role:

Texture - oils can serve to make other ingredients stick together less.

Flavour - while having less flavour than other oils such as safflower oil command premium prices, oils such as olive oil or almond oil may be chosen specifically for the flavour they impart.

Flavour base - oils can also "carry" flavours of other ingredients, since many flavours are present in chemicals that are soluble in oil.

Secondly, oils can be heated, and used to cook other foods. Oils that are suitable for this purpose must have a high flash point. Such oils include the major cooking oils - canola (rapeseed), sunflower, safflower, peanut etc. Some oils, including rice bran oil, are particularly valued in Asian cultures for high temperature cooking, because of their unusually high flash point.

Smoke Points of Oils

Basically, the higher the smoke point, the higher you can heat the oil. For seasoning equipment such as hard-anodised baking tins or terracotta cazuelas and tagines, it is advisable to choose an oil with a higher smoke point than the temperature required to effect the seasoning. The same applies when greasing tins.

Refined oil

Avocado 270ºC / 520ºF

Safflower 265°C / 510ºF

Almond 257°C / 495ºF

Soyabean 232°C / 450ºF

Corn 232°C / 450ºF

Sunflower 232°C / 450ºF

Peanut 232°C / 450ºF

Cottonseed 215°C / 420ºF

Sesame (Light) 210°C / 410ºF

Olive 210°C / 410ºF

Grapeseed 204°C / 400ºF

Rapeseed (Canola) 204°C / 400ºF

Walnut 204°C / 400ºF

Unrefined oil

Sesame 176°C / 350ºF

Olive Oil (Extra Virgin or Virgin) 160°C / 320ºF

Peanut 160°C / 320ºF

Soyabean 160°C / 320ºF

Corn 160°C / 320ºF

Walnut 160°C / 320ºF

Sunflower 107°C / 225ºF

Rapeseed (Canola) 107°C / 225ºF

Safflower 107°C / 225ºF

Flavoured Oils Safety

'Of the two preserving mediums, vinegars are more effective as the acidity kills of most bacteria and they have a longer shelf life than their oil equivalents. It is necessary to heat some oils, especially with chillies and garlic as they can be prone to botulism spores, to around 180ºC/350ºF before pouring into the jar/bottle. This also has the benefit of speeding up the infusion. Alternatively use dried chillies – it tends to be the moisture in fresh chillies (and garlic) that can cause botulism.

Once opened, to be on the safe side as oils also tend to go rancid relatively quickly once exposed to air, keep them in the fridge and monitor them closely for spoilage. They will need to be used up in about 2 weeks. Cold oils are the best ones to use with green herbs.

The shelf life for both oils and vinegars tends to be a shorter than most preserves and they lose some of their flavour after about 4 months.'